Process For Monitoring Territories In Order To Recognise Forest And Surface Fires

ABSTRACT

The monitoring of territories in order to recognize forest and surface fires requires complex automatic and human-assisted processes, which ultimately must include the control of intervention forces. Disclosed are processes for the centralised monitoring of territories. A swiveling and tiltable camera installed at a monitoring site supplies images of overlapping observation sectors. In each observation sector a sequence of images comprising a plurality of images is taken, at an interval which corresponds to fire and smoke dynamics. An on-site image-processing software supplies event warnings with indication of the position of the event site in the analysed image. A total image and an image sequence with image sections of the vent site are then transmitted to a central station and reproduced at the central station as an endless sequence in quick-motion mode. Event warnings with all relevant data can be blended into electronic maps at the central station. Cross-bearing is made possible by blending event warnings from adjacent monitoring sites. False alarms are minimized in that known false alarm sources are marked as exclusion zones in reference images.

The prompt detection of forest and surface fires is crucial for successfully fighting them. To this day, fire watches requiring the deployment of substantial numbers of personnel are set up in many territories at times when fires are likely to erupt, involving the visual observation of the territory from elevated vantage points or dedicated towers.

The detection of fires and/or smoke in outdoor areas by technical means has developed to some sophistication and a variety of options.

Earlier systems mostly evaluate the IR spectrum, mainly using sensor cells. For reasons of cost, IR cameras are used less frequently. A typical representative is the system described in [1] (U.S. Pat. No. 5,218,345), which uses a vertical array or line of IR detectors. This detector array is positioned in front of a reflector for horizontal swivelling together with it so as to scan a territory. The sensitivity of the sensors within the array is graded to prevent an over-emphasis of the foreground relative to the near-horizon areas.

[2] (DE 198 40 873) describes a process which uses different types of cameras and evaluates the visible spectrum. The parallel application of several different methods of analysis makes possible the detection of both fire and smoke. An essential feature is the comparison of reference images in memory with current images by way of generating differential images and by the application of analysis algorithms to the latter, with evaluation focussed on texture properties, above all.

For detection, the system described in [3] (U.S. Pat. No. 5,289,275) evaluates relative colour intensities in the visible spectrum in addition to the TIR range (thermal infrared range), based on the assumption that, in particular, the Y/R (yellow to red) and B/R (blue to red) ratios contain features significant for fire detection.

The systems described in [4] (U.S. Pat. No. 4,775,853) and [5] (U.S. Pat. No. 5,153,722) evaluate the IR, UV and visible ranges of the spectrum in combination, assuming in particular that a significant ratio of the IR and UV intensities is indicative of fire.

These and various other publications not mentioned above are concerned exclusively with means and methods for the direct outdoor fire and/or smoke detection, i.e. under open-country conditions and over great distances. Procedures involving a complex monitoring of territories are not taken into consideration. Methods of this type must include at least one of the aforesaid processes for automatic fire and/or smoke detection and, in addition, must be designed to co-operate with further automatic or personnel-operated processes up to and including the issuing of instructions to firefighting crews.

The object underlying the present invention is to overcome the limitations of the existing methods and to implement a method for the complex monitoring of territories for forest and surface fire detection which embraces one of the aforesaid approaches. This object is attained by using the features set forth in patent claim 1.

For outdoor fire and/or smoke detection, the invention embraces a method as described in DE 198 40 873. As a matter of principle, however, the inventive solution is not exclusively linked to that method and allows for the use of other detection methods also.

For the monitoring of territories for forest and/or surface fire detection, the invention provides for the setting up of at least one—and preferably a plurality of—observation sites of which the observation areas overlap. The observation sites require an elevated position for installing a camera, preferably a CCD matrix camera, in a swivel-and-tilt mount. If omnidirectional view through 360° is required, the camera must be installable at the highest point of the camera site. Such sites may be dedicated masts, existing forest fire watch towers or communication mast structures, etc. The observation site includes a control and evaluation unit running image processing software for fire and/or smoke detection in an image as well as control software, and is equipped with picture and event memory and an interface to communication equipment. Further, the control software includes modules for image manipulation and the generation of panoramic views.

Themselves set up for unmanned operation, the observation sites are linked to a manned central station, the latter including a computer unit comprising an operating, display and monitoring workplace, control software, event and image memory space, means for mixing and displaying images on at least one monitor, as well as interfaces to communication equipment.

A communication unit for communicating images, data and control information, and including an audio service channel to firefighting crews present at the observation site, serves to connect the latter with the central station. Such crews may use permanent or semi-permanent ISDN lines, Internet access or dedicated radio links.

Additionally, the central station has available radio means for communicating with and passing operating instructions on to mobile firefighting crews. The crews are equipped with positioning means such as GPS devices, with their positions automatically transmitted to the central station by said radio means and the intervals between position reports matched to the speed of travel typical of such crews.

According to the inventive method, the system is operated in accordance with the features in patent claim 1. An essential aspect comprises process steps i) and j), in which an image sequence of an event is presented to the operator in a fast-motion mode. This way, the connection between automatic detection and subjective evaluation can be realized in a particularly effective manner.

The methods in patent claims 7 to 11 can be assigned to the same aspect. As described in claim 7, the central station has available to it electronic maps and/or digitized and memorized aerial photographs of the territories monitored, referred to generally as “maps” hereinafter. A constituent part of the control software is software for zooming and scrolling co-ordinate-based electronic maps and for inserting co-ordinate-based data. The maps are displayed automatically in response to incoming messages (see claim 1 h)) or to messages having alert status, or in response to manual request in the case of messages not having alert status, with information identifying the observation site, the observation sector, the direction and the estimated distance to the event location being inserted in the map automatically in a graphic or alphanumeric data format and with the representation following the processes defined in claim 11. As described in claim 8, if two or more messages arrive at the same or almost the same time from neighbouring observation sites in accordance with claim 1h), the information in all these messages is displayed in a map in order to enable a cross bearing to be derived.

As described in claim 9, if simultaneous or near-simultaneous messages from adjacent observation sites are absent, it is possible to insert them in the map by manual request, with the operator him- or herself determining potentially pertinent observation sectors. This way, manual images may be called down from these observation stations later on and be included in a subjective evaluation.

As stated in claim 10, firefighting crews are equipped with position determining means such as GPS devices, with their positions and identifications transmitted automatically to the central station via the aforesaid radio link. In the cases described in claims 7 to 9, positions and identifications are automatically inserted in the map in a graphic or alphanumeric format. Regardless of event messages, this information is displayed automatically in response to manual map call-up requests also.

FIG. 1 shows a possible implementation of data and representations inserted in a map in accordance with the claims 7 to 11. For reasons of clarity, the underlaid map itself is not shown in the drawing.

The Figure shows an observation site identified by a site identifier 1, with the event message from this site assumed to have been the first message as defined in claim 1h) and represented by a direction vector 5 with an estimated distance range 6. The event message from the observation site identified by the site identifier 2 is represented by direction vector 7 and an estimated distance range 8. It does not matter whether the respective event message corresponds to the methods described in claim 8 or 9. Evidently and understandably, the distance estimate on the basis of a two-dimensional image is subject to substantial uncertainty; yet the utility of the information displayed can be enhanced considerably by deriving a cross bearing from the direction information.

The Figure also shows for each observation site the observation sectors 3, their identification numbers as well as their boundaries 4. The representation ignores that the observation vectors are in fact slightly broader to ensure some overlap. The width of the observation sectors depends on the horizontal aperture angle of the camera lenses and may be varied by selecting lenses having different focal length. The selection is determinded above all by the structure of the territory to be monitored.

The Figure also shows the position and the identication of a firefighting crew 9.

Further essential aspects of the inventive solution are to ensure the rapid processing of data by the image processing software for smoke and/or fire detection and to minimize the number of false alerts.

The processing of data by the image processing software requires considerable computing power and time. In order to minimize this effort and time, data reduction is performed as described in claims 2 and 3 before the data is passed on to the image processing software.

The method of claim 2 starts out from the fact that, in a two-dimensional image, perspective distortion causes the foreground to appear to be enlarged; for this reason, the image provides a very high resolution in this area although the task to be accomplished does not require it. In accordance with the invention, no data reduction takes place in the horizontal direction; in the direction toward the foreground, data reduction is increased in steps as finely graded as possible, with the finest grade given by the pixel structure of the image.

In accordance with the method of claim 3, image portions which do not contribute to a solution of the underlying problem are not passed on to the image processing software. The vertical image boundary in the top image region crops unnecessary image portions of the sky, retaining a minimum sky area above the horizon as smoke is most clearly detected before a background sky. The vertical image boundary in the bottom image region crops unnecessary foreground areas, which it would be meaningless to input to the routine even if data reduction using the method of claim 2 were applied.

Vertical image boundaries can be entered separately for each observation sector of the observation site. This may be combined with a separate adjustment of the camera tilt angle for each observation site. This adjustment is particularly relevant to mountain areas where observation sectors of a observation site may be directed down into a valley or up against a mountain slope.

As described in claim 8, vertical image boundaries and camera tilt angle are manually set at the central station based on the images transmitted from the observation site. Insertions are made directly into the images, are communicated by the central station's control software to the control software of the observation site, and are memorized at both locations. The control software makes possible the insertion of graphic information into the displayed images. The control software memorizes the types and positions of the graphic elements as data files associated with the respective image.

The method of minimizing the number of false alerts is described in claim 12. So-called exclusion areas are defined manually at the central station on the basis of the images communicated from the observation site. Insertions are made directly into the images, are communicated by the central station's control software to the control software of the observation site, and are memorized at both locations. In this respect, reference is made to the description hereinabove of the vertical image bounding process. Exclusion areas may be defined as polygons of any shape, thus ensuring a good match to existing conditions. At the central station, it can be determined, and communicated to the observation site, whether an event message pertaining to an exclusion area is to be reported to the central station. Such messages, if transmitted, are not assigned an alert status.

[1] U.S. Pat. No. 5,218,345

[2] DE 198 40 873

[3] U.S. Pat. No. 5,289,275 [4] U.S. Pat. No. 4,775,853 [5] U.S. Pat. No. 5,153,722 

1. A process of monitoring territories for forest and surface fire detection, based on a first complex of means stationed at a minimum of one monitoring site, said complex comprising a camera mounted at an elevated location with the ability to tilt and swivel, the horizontal swivel range being at least 360°, and control and evaluation means connected to the camera and running image-processing software for detecting smoke and/or fire in the images the camera provides, control software, event and image memory, and an interface to communication means; a second complex of means installed at a manned central station and comprising a computer including an operating, display and monitoring workplace, control software, memory for events and images, means for mixing and outputting images to at least one monitor, and at least two interfaces to communication means; first bidirectional communication means for image files, data, and voice to interconnect said first and second complexes; and second bidirectional data and voice communication means to connect said second complex with deployed firefighting crews, characterized in that, in accordance with the following steps, a) the observation area of a monitoring site is divided into observation sectors each corresponding to the horizontal aperture angle of the camera lens; b) the horizontal angular distance between adjacent observation sectors is selected to create an overlap between them; c) the camera is aimed by positioning means at said observation sectors in automatic succession or in any order under manual control from the central station; d) the camera, having been aimed, provides a plurality of images timed for adaptation to the dynamics of smoke and fire; e) the images are communicated to the control unit for storage as an image sequence; f) the images are input by the control unit to the image processing software for smoke and/or fire detection, the image processing software responding to the presence of smoke and/or fire by issuing an event message and data relating to the position and magnitude of the event; g) if an event message is generated, the control software marks the event location in one of the pertinent images on the basis of the data concerning the location and magnitude of the event, and proceeds to compress the image and to transmit it to the central station together with an alert message comprising the identity of the monitoring site, the observation sector, the direction of and the estimated distance to the event location; h) the alert message received at the central station is reproduced visibly or audibly and the image decompressed, stored and displayed either automatically or in response to manual request; i) at the central station, a manual request can be entered and communicated to the monitoring site, which causes its control software to extract from the images of the current image sequence the image portions corresponding to the marked event location, to compress them, and to communicate them as an image sequence to the central station; j) when received at the central station, the images of the image sequence corresponding to step (i) are decompressed, stored, and displayed as an endless sequence in a fast-motion display mode, and said sequence is inserted into the overall image of step (g) or displayed by itself in a large-scale format.
 2. Method as in claim 1, characterized in that the control unit of the monitoring site a) divides the image into several horizontal image strips before communicating a video image to the image-processing software according to step 1(f); b) averages sets of several pixels from image strips below the horizon, but not including the horizon itself, with the number of pixels so averaged increasing between image strips in a direction toward the bottom image edge; c) inputs the data-reduced images thus obtained to the image-processing software for smoke and/or fire detection; and d) de-distorts the data on the position and magnitude of the event location the image-processing software has returned, such de-distortion using steps which are the inverse of (b) and (a), and then inserts the data into the original image.
 3. Method as in claim 1, characterized in that the control unit a) crops the image vertically by removing from its top and/or bottom edges horizontal image strips not relevant to the detection of forest fires and does so before communicating the image to the image-processing software according to step 1(f); b) inputs the data-reduced images thus obtained to the image-processing software for smoke and/or fire detection; and c) inserts into the original image the data on the position and magnitude of the event location returned by the image processing software, taking the manipulations of step (a) into account.
 4. Method as in claim 1, characterized in that the vertical image crop of step 3(a) can be pre-defined for each observation sector.
 5. Method as in claim 1, characterized in that the vertical image crop can be combined with a different camera tilt for each observation sector individually.
 6. Method as in claim 1, characterized in that, at the central station, a) the images from observation sectors, or a panoramic image with the observation sectors marked, from a monitoring site are called up manually at the operating, display and monitoring workplace of the computer unit; b) the vertical image crop and the tilt of the camera defined for each observation sector are entered by means of the control software into the individual sector images or into the panoramic image; c) the control software determines the parameters of such entries and communicates them to the control software of the monitoring site; d) step (a) is repeated to check the measures of steps (b) and (c) for correctness and, optionally, to repeat the measures corresponding to (b) and (c) to increase the precision.
 7. Method as in claim 1, characterized in that the central station has electronic maps and/or digitized and stored aerial photographs, referred to generally as “map” hereinafter, of the areas monitored, displays the pertinent map automatically or in response to manual request in response to a message according to step 1(h) being received, and automatically inserts into that map the data comprising the identity of the monitoring station, the observation sector, the direction, and the to estimated distance to the event location in a graphic and an alphanumeric data format.
 8. Method as in claim 1, characterized in that, when two or more messages according to 1(h) are received at the same or nearly the same time from adjacent monitoring sites, the information contained in all said messages is displayed on the map so that a cross bearing can be taken.
 9. Method as in claim 1, characterized in that a) the displayed information can be expanded to adjacent monitoring sites by zooming and shifting the displayed portions of the map; b) the adjacent monitoring sites and their observation sectors can be displayed in response to manual request; c) the observation sectors of adjacent monitoring sites which are relevant to the received messages according to 1(h) are determined from the map; d) current images of the observation sectors so determined of an adjacent monitoring site can be called up manually at the operating, display, and monitoring workplace of the computer unit; e) the images so obtained are analyzed visually for features the image processing software for smoke and/or fire detection failed to identify as an event; f) the location of a visually detected or suspected event is marked in the image by the control software; g) the control software derives a message corresponding to 1(h) from the entry so performed; and h) the message thus derived is subjected to further treatment.
 10. Method as in claim 1, characterized in that a) mobile firefighting crews are equipped with position determining means such as GP5 devices; b) the deployed vehicles communicate their current positions by radio to the central station on an automatic and continuous basis; c) upon automatic or manual call-up of a map, the positions of deployed vehicles located in the displayed area are automatically shown on the map in a graphic and alphanumeric data format.
 11. Method as in claim 1, characterized in that the display of image and the map can occur selectively according to the split-screen principle or separately on two different screens.
 12. Method as in claim 1, characterized in that the sources of false alerts such as settlements, streets and roads, the surfaces of bodies of water or other elements where smoke or confusing light effects may occur are eliminated by a) manually calling up and displaying at the central station images of observation sectors, or a panoramic image with the observation sectors marked, of a monitoring site, b) causing the control software to outline by a polygon of any suitable shape the portions of an individual image, or of a panoramic image, which may lead, or have previously led, to false alerts; c) causing the control software of the central station to determine the parameters of such entries and to communicate them as exclusion areas to the control software of the monitoring site; d) determining manually at the central station whether event messages pertaining to exclusion areas are to be reported to the central station and causing the control software at the central station to communicate such determinations to the control software of the monitoring site; e) in case the image processing software issues a message according to step 1(f), the control software of the monitoring site checking whether the message pertains to an exclusion area; and f) in case a message pertains to an exclusion area, the control software of the monitoring site proceeding in accordance with step 1(g) if instructed to report the messages to the central station, but without assigning an alert status to such message.
 13. Method as in claim 3, characterized in that the vertical image crop of step 3(a) can be pre-defined for each observation sector.
 14. Method as in claim 3, characterized in that the vertical image crop can be combined with a different camera tilt for each observation sector individually.
 15. Method as in claim 4, characterized in that the vertical image crop can be combined with a different camera tilt for each observation sector individually.
 16. Method as in claim 3, characterized in that, at the central station, a) the images from observation sectors, or a panoramic image with the observation sectors marked, from a monitoring site are called up manually at the operating, display and monitoring workplace of the computer unit; b) the vertical image crop and the tilt of the camera defined for each observation sector are entered by means of the control software into the individual sector images or into the panoramic image; c) the control software determines the parameters of such entries and communicates them to the control software of the monitoring site; d) step (a) is repeated to check the measures of steps (b) and (c) for correctness and, optionally, to repeat the measures corresponding to (b) and (c) to increase the precision.
 17. Method as in claim 1, characterized in that, at the central station, a) the images from observation sectors, or a panoramic image with the observation sectors marked, from a monitoring site are called up manually at the operating, display and monitoring workplace of the computer unit; b) the vertical image crop and the tilt of the camera defined for each observation sector are entered by means of the control software into the individual sector images or into the panoramic image; c) the control software determines the parameters of such entries and communicates them to the control software of the monitoring site; d) step (a) is repeated to check the measures of steps (b) and (c) for correctness and, optionally, to repeat the measures corresponding to (b) and (c) to increase the precision.
 18. Method as in claim 7, characterized in that, when two or more messages according to 1(h) are received at the same or nearly the same time from adjacent monitoring sites, the information contained in all said messages is displayed on the map so that a cross bearing can be taken.
 19. Method as in claim 7, characterized in that d) the displayed information can be expanded to adjacent monitoring sites by zooming and shifting the displayed portions of the map; e) the adjacent monitoring sites and their observation sectors can be displayed in response to manual request; f) the observation sectors of adjacent monitoring sites which are relevant to the received messages according to 1(h) are determined from the map; d) current images of the observation sectors so determined of an adjacent monitoring site can be called up manually at the operating, display, and monitoring workplace of the computer unit; e) the images so obtained are analyzed visually for features the image-processing software for smoke and/or fire detection failed to identify as an event; f) the location of a visually detected or suspected event is marked in the image by the control software; g) the control software derives a message corresponding to 1(h) from the entry so performed; and h) the message thus derived is subjected to further treatment.
 20. Method as in claim 7, characterized in that d) mobile firefighting crews are equipped with position determining means such as GP5 devices; e) the deployed vehicles communicate their current positions by radio to the central station on an automatic and continuous basis; f) upon automatic or manual call-up of a map, the positions of deployed vehicles located in the displayed area are automatically shown on the map in a graphic and alphanumeric data format. 